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Lookin' mighty fancy....BUT do you have any plans to actually test the units with significant difference between solar panel voltage and battery voltage??
At least with the above pictures, the hacked unit is doing...basically nothing except limiting current. On one screen, the input voltage and output voltage differ by 0.8v; on the other, the difference is 1.1v. Keep in mind that a diode's forward voltage drop is generally between 0.6v and 1.2v depending on the current flow--and in the non-synchronous buck conversion topology, ALL the output power has to flow through the diode.
If you had regulation headroom voltage, an MPPT sweep curve at full sun would be expected to look something like this (grabbed from Google Images). It should be quite obvious where the max power point is.
<img data-ratio="52.99" style="width:451px;height:239px;" width="451" alt="?u=https%3A%2F%2Ftse3.mm.bing.net%2Fth%3Fid%3DOIP.iPn8lFgAS7VgiMZ6xSKPwgAAAA%26pid%3DApi&f=1" data-src=" https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse3.mm.bing.net%2Fth%3Fid%3DOIP.iPn8lFgAS7VgiMZ6xSKPwgAAAA%26pid%3DApi&f=1" src="/applications/core/interface/js/spacer.png">
I've probably asked this before, but do you happen to have a decent oscilloscope for bench testing/measurements?
nothing I can do about it..as far as I know..originally msb used 40khz switching freq.. I found that 20khz actually works better--less heating..so I used 20khz..
Without digging into it myself, I would wonder if the switching frequency used would be dependent on the voltage difference. If the inductors saturate, you would need a higher switching frequency to avoid stressing caps/etc. and keep the output ripple down.
greetings.. well I have several different configurations of solar panels feeding two separate msbs..
one has two identical solar panels stacked.. they are OC 45v, Pmax 36v panels..so I get 70v more-or-less heading intothat msb..
the other msb is fed with a whole bunch of old hail-damaged panels..they stackup to 100v give or take..The curve u have shown is for ONE solar panel in perfect conformal sunlight across the entire panel.. my panels have partial shading sometimes and are combined panels,so u can see the result in my power curve picture...multiple peaks..every few minutes I rescan to make sure I am dithering around the best peak..
no I dont have a good scope anymore..wish I did..my 465 puked out some years ago.. I dont do enuff tech stuff anymore so I havent looked for a replacement..all I have is some rediculous digital dso cheapy.. works enuff to see my pwms pulses to verify its working..I have freq counter..
the output voltage does NOT allgothru any series diode.. the FET is the series device.. the clamp diodes arejust from switching to ground..asynch style..
forgot to mention-- I have 20 100AH NiFe battery stack..so my voltages are BULK=34v, FLOAT=33v more or less..they really dont care much..it boils down to how often do u want to add more H2O
The next step that wouldmake this project nice is to add wifiand an android app..
so the Adafruit QT PY can be replace with same footprint https://www.adafruit.com/product/5325 which has the wifi..also it hosts a position on the bottom side for a 2M SSD eprom..so running data could be collected and then displayed on a wifi app..
if anyone had both time and interest in doing that, I would gladly send them a fully built makeskybluer ..and a list showing where to jumper to to pickup the necessary inputs/outputs/power and gnd.. otherwise I supposeI will stumble along and try to do that too.. notmy interest.. I am more interested in refining the mppt routine to more quickly accomodate for weather conditions and thereby boost the collected energy overall..
also -- forgot to reply correctly to the question about higherinput voltages.. my present configuration --in early morning, late evening sunlight-- the PV voltage willrise dramatically when scanning for the peak watts.. true mppt occuring during low amps operation..to be honest, it appears to me that these torroids are small size and really not effective for amperage greater than a few amps, maybe 5 amps at the most..after that,as I have said,it just becomes a matter of winding resistance being far more a factor than inductance.. look at the small size of these inductors..u cant get blood out of a turnip..
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it appears to me that these torroids are small size and really not effective for amperage greater than a few amps
I get 6.4 amps most of the day and the most is 7.9 amps . My input to the MSB is 124v DC . I now get over 12 hours of sunlight .
Right!!.. at 500+ watts coming in, there is NO peak.. lol.. just pure resistance of the (too-small)torroid..
also I should explain-- when the current is heavy, since msb isnt using remote sensing of current, voltages, the apparent currents are artificially high --due to in-circuit resistance -- which could be accomodated for..I just havent done that yet..so when it reads 15 amps, in reality its probably more like 10 or 12 amps..
the biggest 'lump' of series resistance that forces error into the current/voltage readings is the internal resistance of the circuit breakers..depending on the mfger and the amperage rating, these will vary alot..then also the wiring to the actual battery adds to the overall in-series-resistance that forces the error in the readings.. fortunately all this is simply a linear function.. so I will add a 'comp' factor to somewhat correct for the error in all the readings, dependent ONLY on PVi and BATTi ..
it wont be perfect,but I think it can be a reasonable correction..without having to somehow redo everything and require remote sensing of everything..
Lookin' mighty fancy....BUT do you have any plans to actually test the units with significant difference between solar panel voltage and battery voltage??
Thats probably why they chose 40Khz.. but 40khz produces twice the edge transitions of 20khz that I am using.. and I chose 20khz simply because I noticed the overall heating produced was noticably reduced using only 20khz.. so many balls in the air at the same time..it might require more investigation due to so many things inter-acting..
also--u were correct--in a way-- they(msb) went the extramile and added quite alot of stuff to make sure PVin did NOT go anywhere IF the onboard power supply wasnot LIVE.. in the pic..u might be able to see the tiny transformer ..it is ther to simply transfer the screaming switching freq of the power supply switcher to a heavy FET on the PV input.. no switching--noPV in..so maybe thats what u were thinking of when u talked about the in-line diode.. its also a FET in these msbs..sweet..
it appears to be fixxed at 40khz.. they(msb) most likely are using pretty cheap FETs in order to push this product out at this amazing low price-point.. they must have chosen 40khz as a compromise freq , best choice for the under-sized torroid, and just run some heat on the cheap FETs..what-the-hell we got a great fan!!..
so maybe thats what u were thinking of when u talked about the in-line diode..
No, the on-board buck converters comprise of a FET and a flyback diode. This diode will drop 0.6-1.2v depending on the current flowing through it.
If they'd used a synchronous buck converter topology, said diode would be replaced with a FET for reduced power losses.
<img alt="PPT - DC-DC Fundamentals PowerPoint Presentation - ID:1595391" data-ratio="75.00" style="width:349.333px;height:262px;" width="720" data-src=" 
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worth noting that if the PWM freq is too low, you'll basically end up with a PWM charge controller...with no "buck" functionality. That will reduce losses...as if the inductor doesn't "ring", the diode won't be doing anything.
Still...without any significant voltage headroom (<10v), you technically don't have an MPPT in the first place.
also--u were correct--in a way-- they(msb) went the extramile and added quite alot of stuff to make sure PVin did NOT go anywhere IF the onboard power supply wasnot LIVE.. in the pic..u might be able to see the tiny transformer ..it is ther to simply transfer the screaming switching freq of the power supply switcher to a heavy FET on the PV input.. no switching--noPV in..so maybe thats what u were thinking of when u talked about the in-line diode.. its also a FET in these msbs..sweet..
Betcha there's also separate taps on that little transformer to drive both of the main switching FETs as well...they'll each need a floating gate power supply (if they were designed to be driven out of phase).
Betcha there's also separate taps on that little transformer to drive both of the main switching FETs as well...they'll each need a floating gate power supply (if they were designed to be driven out of phase).
I will investigate that and get back...
Lookin' mighty fancy....BUT do you have any plans to actually test the units with significant difference between solar panel voltage and battery voltage??
At least with the above pictures, the hacked unit is doing...basically nothing except limiting current. On one screen, the input voltage and output voltage differ by 0.8v; on the other, the difference is 1.1v. Keep in mind that a diode's forward voltage drop is generally between 0.6v and 1.2v depending on the current flow
The readings are disturbing as my input voltage is 62 v and the output is 30 v and 236 watts . My other MSB input voltage is 124 v and output is 66 v and 523 watts .